How does Impala Implements GroupBy Extension(CUBE, ROLLUP and GROUPING SETS) In a distributed way?

I’m Learning how to Implement GroupBy Extension(CUBE, ROLLUP and GROUPING SETS), I’ve watched at FE several times, But I still can’t understand how to use grouping_ids to implement GroupBy Extension throught collaboration with BE in a distributed way.How is it to collaborition with ExchangeNode? Is it collaborition with ExchangeNode?

Can someone help me with the maze？

Answer

Impala introduced the group by modifiers in 7.2.2:

Added support for GROUP BY ROLLUP, CUBE and GROUPING SETS. The GROUP BY ROLLUP clause creates a group for each combination of column expressions. The CUBE clause creates groups for all possible combinations of columns. The GROUPING SETS just lets you list out the combinations of expressions that you want to GROUP BY.

This is explained in the documentation for GROUP BY starting with that version.